1. Field of the Invention
This invention relates to an image forming apparatus wherein an image on a document is converted to an electrostatic latent image by an electrostatic image forming process and the latent image is developed by toner, and a toner image is printed out on a sheet material.
2. Description of the Related Art
An image forming apparatus, e.g., a copying machine, has an image reading section for reading an image on a document, an image forming section for forming an image read by the image reading section, and a material transporting section for transporting sheet materials to output a toner image formed by the image forming section.
The reading section has a document table on which a document is mounted, reads image data of the image on the document, and transmits data to the image forming section.
The material conveying section includes at least one of material cassette or multi feeder, which can supply sheet materials having types of sizes, a large capacity cassette which can contain a large number of sheet materials and a multi-stage paper conveying device having a plurality of cassettes each contains sheet materials having types of sizes. The material transporting section supplies paper having a desired size to the image forming section.
The image forming section has a photoconductive drum, a developing device, and a copy start switch. The photoconductive drum forms an electrostatic latent image in accordance with image data. The developing device supplies toner to the latent image formed on the photoconductive drum, thereby developing the image. The copy start switch designates the copy start in order to start the image formation. The image forming section forms the image on the document on the paper conveyed by the material conveying section.
In the above copying machine, the large capacity cassette is normally selected as a standard state by initialization.
In some large-sized high speed copying machines, a document size sensor for detecting the size of the document and a function of an automatic magnification selecting mode are provided. For inputting a paper size automatic selection mode for selecting a cassette, which contains paper whose size is conformed to the size of the document, or the large capacity cassette, and magnification for enlargement or reduction, the automatic magnification selecting mode selects the cassette in which paper whose size is defined in accordance with the copy magnification and the document size or the large capacity cassette is selected.
However, for forming an image on the paper whose size is different from the size of the paper contained in the large capacity cassette selected by the initialization, a cassette containing a suitable paper must be newly designated.
Moreover, even if it is obvious that the image is formed on the paper whose size is different from the size of the paper contained in the large capacity cassette and paper is added to the cassette containing the paper having the corresponding size, a cassette in which paper is added must be newly designated.
On the other hand, even if the specific cassette is selected by the paper size automatic selecting mode or the automatic magnification selecting mode, the operation procedure becomes complicated in accordance with the increase in the number of functions of the copying machine when it is required that the image is formed on the paper whose size is the same as the document. In other words, for example, the following operation procedure is required.
The automatic magnification selecting mode is operated to conform to the size of the paper contained in the large capacity cassette regardless of the user's intention. The user cannot judge the size of the document and the the paper having the size which the user wishes to copy is compared with the paper contained in the cassette. Due to this, the paper size automatic selecting mode or the the automatic magnification selecting mode must be released.
Moreover, there is a case that the user does not always understand the size of the paper displayed by A4 or A5. Due to this, there is a problem in that a paper having an erroneous size is selected and an undesirable copying material is provided.